THE MAEINE AQUABIUM 57 



Various mixtures have been suggested for this purpose, and 

 among them the following are perfectly satisfactory : 



1. Litharge 2 parts 



Fine sand 2 



Plaster of Paris . . . . . 2 ,, 



Powdered resin 1 part 



Mix into a very thick paste with boiled linseed oil and a little 

 driers. 



2. Bed lead 3 parts 



Fine sand 3 



Powdered resin . . . . .1 part 



Mix with boiled linseed oil as above. 



Both these cements should be applied very liberally, and the 

 aquarium then allowed to remain quite undisturbed for at least two 

 weeks before any water is introduced. 



FIG. 37. HEXAGONAL AQUARIUM CONSTRUCTED OP ANGLE 

 ZINC, WITH GLASS SIDES 



When ready for the water, the bottom of the aquarium should 

 be covered with a moderately thick layer of fine sand from the 

 sea shore, and stones then piled in such a manner as to form little 

 tunnels and caves to serve as hiding-places for those creatures that 

 prefer to be under cover. As to the selection of stones, we have 

 already suggested that some may have weeds rooted to them, and 

 that pieces of rock with anemones, sponges, and other forms of life 

 attached may be chipped off. Further, on many of our rocky 

 coasts we may find, near low-water mark, a number of stones 

 covered with a layer of vegetable growth, amongst which many 

 small animals live, often more or less concealed by their protective 



